With some modification, the infrastructure of existing power distribution systems may be used to provide data communication services to customer premises. In a power line communication system (PLCS), existing power lines that already have been run may be used to carry data signals to and from homes, offices, and other structures. These data signals are communicated on and off the power lines at various points in the power line communication system, such as, for example, near homes, offices, Internet service providers, and the like.
Power distribution systems include numerous sections, which conduct power at different voltages. The transition from one section to another typically is accomplished with a transformer. For example, high voltage power transmission lines are converted to medium voltages in the range of 1,000V to 100,000V and may carry 200 amps or more.
The sections of the power distribution system that are connected to the customers premises typically are low voltage (LV) sections having a voltage between 100 volts (Vrms, 60 Hz, or “V”) and 240V, depending on the system. In the United States, the LV power lines are about 120V. The transition from an MV section to an LV section of the power distribution system typically is accomplished with a distribution transformer, which converts the higher voltage of the MV section to the lower voltage of the LV section.
Power line communication systems generally communicate over low and/or medium voltage power lines. As power line communications proliferate, there are increasingly more power line communications traversing the power lines among more power line communication devices. A given data signal may traverse an intended path from a source to a destination. However, the same data signal also may traverse additional unintended paths. Thus, some data signals may be received by devices, which are not the intended receiving device (hereinafter the “unintended receiving device”). The reception of data signals by devices that are not the desired receiving device may have one or more undesirable consequences. For example, the unintended receiving device may be contemporaneously receiving data transmitted from another source in the same frequency band. Thus, the unintended data signal will, in essence, be interference (e.g., noise) to the data signals that are intended for the receiving device. As another example, the data signals may be received by the unintended device, which may attempt to demodulate and decrypt the data signal. This may increase latency of communications through the unintended receiving device. Further, in some instances the transmitting device may undesirably receive the transmitted data signal. Security is yet another issue. One adverse effect may be decreased performance of a portion or sub-network of the power line communication system. In summary, data signals received (whether as noise or data) by unintended devices may degrade network performance.
Consequently, there is desire to prevent data signals from being received by unintended devices. One solution is to allocate different frequency bands for each device (e.g., employ a frequency division multiplexed system). However, in many systems this architecture is impossible or impractical. Another solution is to utilize a data signal attenuator device that attenuates data signals. Power line communications employ the existing power lines to provide communications. It is impractical to cut power lines to insert filters for attenuating data signals. Consequently, one well-known means of attenuating data signals is to place a magnetically permeable toroid around the power line, which acts as an inductor thereby attenuating high frequency data signals. However, the power lines carry high voltages and high currents. The high currents of the power lines often saturate the toroid thereby reducing its effectiveness for attenuating data signals. One solution is to make the toroid bigger or to include an air gap to reduce the likelihood of saturation. However, larger toroids, which are typically constructed of ferrite, become too heavy and/or large for practical deployment. Providing an air gap in the toroid simply reduces the effectiveness for attenuating data signals by reducing its inductance.
Accordingly, there is a need for providing a data signal attenuator device that can be utilized without splicing existing power lines, that does not saturate due to the high current carried by the power line, that is sized for practical deployment, and that is economical for wide deployment. One or more of embodiments of the present invention address one or more of these and other needs and provide advantages for power line communication systems.